MONTREAL (Reuters) - The United Nations aviation agency is not considering the creation of a “no-fly” zone around North Korea because the direction of Pyongyang’s tests are not predictable, two sources familiar with the organization’s thinking said on Thursday.

Airlines are already avoiding North Korean airspace and some have re-routed flights to avoid portions of the Sea of Japan because of the missile tests.

European carriers Air France KLM SA and Lufthansa did so in August, while Singapore Airlines Ltd on Friday said its flight routings did not traverse near the missile trajectories because it had been avoiding the northern part of the Sea of Japan since July.

Cathay Pacific Airways Ltd on Monday said the crew of a San Francisco-Hong Kong flight reported a suspected sighting of a missile re-entry from North Korea’s latest test on Nov. 29.

In a statement, the airline said the aircraft was far from the location and there were no plans to change flight routes at this stage. Data from flight tracking website FlightRadar24 shows the CX893 flight path was over land in Japan, to the east of the Sea of Japan.

OPSGROUP, which provides safety guidance to airlines, said in September that the western portion of Japanese airspace is a risk area due to multiple North Korean missile re-entries into the same area, according to its website.

International Air Transport Association (IATA) director general Alexandre de Juniac was quoted in the South China Morning Post on Thursday saying that the International Civil Aviation Organization (ICAO) “could declare a no-fly zone” in the region.

Montreal-based ICAO cannot impose rules, such as ordering countries to close their domestic airspace, but regulators from its 191-member states almost always adopt and enforce the standards it sets for international aviation.

ICAO has condemned North Korea for launching missiles without notice, a move that could represent a threat to commercial flights.

The missile tests are worrisome for civil aviation authorities in the wake of the 2014 downing of Malaysia Airlines Flight MH17 over Ukraine. So far, North Korea has not heeded requests by ICAO to give advance notice of any launches, one of the sources said.

An IATA spokeswoman said by email on Thursday that de Juniac’s remarks were in reference to the airline trade group’s support of a recent decision by ICAO to “strongly condemn North Korea’s continued launching of ballistic missiles over and near international air routes.”

While ICAO has urged airlines to take precautions, the agency is not advocating for a no-fly zone, because such a move would be disruptive for carriers and it’s not clear where North Korea will fire missiles during tests.

“It is so random, it (a no fly zone) becomes ineffective,” one of the sources said.

Both sources spoke on condition of anonymity because they were not authorized to talk with media. An ICAO spokesman was not immediately available for comment.

Tensions in the region have risen markedly in recent months after repeated North Korean missile tests in defiance of U.N. sanctions and the detonation of what Pyongyang said was a hydrogen bomb on Sept. 3.

On Thursday, two American B-1B heavy bombers joined large-scale combat drills over South Korea.